Platinum nanoparticle functionalized fibrous hierarchical zeolite and method of making the same

ABSTRACT

A functionalized fibrous hierarchical zeolite includes a framework comprising aluminum atoms, silicon atoms, and oxygen atoms, the framework further comprising a plurality of micropores and a plurality of mesopores. A plurality of nanoparticles comprising platinum are immobilized on the framework.

TECHNICAL FIELD

The present disclosure generally relates to porous materials and, morespecifically, to zeolites.

BACKGROUND

Materials that include pores, such as zeolites, may be utilized in manypetrochemical industrial applications. For example, such materials maybe utilized as catalysts in a number of reactions which converthydrocarbons or other reactants from feed chemicals to productchemicals. Zeolites may be characterized by a microporous structureframework type. Various types of zeolites have been identified over thepast several decades, where zeolite types are generally described byframework types, and where specific zeolite materials may be morespecifically identified by various names such as ZSM-5 or beta-zeolite.

BRIEF SUMMARY

The present application is directed to functionalized zeolites. Suchfunctionalized zeolites may, according to various embodiments, includeplatinum nanoparticle functionalization. Such functionalized zeolites,according to one or more embodiments presently disclosed, may haveenhanced or differentiated catalytic functionality as compared toconventional zeolites. Additionally or alternatively, the functionalizedzeolites may be useful as zeolite substrates upon which additionalchemical transformations may take place.

In accordance with one or more embodiments of the present disclosure, afunctionalized fibrous hierarchical zeolite includes a frameworkcomprising aluminum atoms, silicon atoms, and oxygen atoms, theframework further comprising a plurality of micropores and a pluralityof mesopores. A plurality of nanoparticles comprising platinum areimmobilized on the framework.

In accordance with one or more embodiments of the present disclosure, amethod for making a functionalized fibrous hierarchical zeolitecomprising a plurality of nanoparticles comprising platinum includescontacting a functionalized fibrous hierarchical zeolite comprisingisolated terminal organometallic functionalities comprising platinumwith an atmosphere comprising H₂. The fibrous hierarchical zeoliteincludes a framework comprising aluminum atoms, silicon atoms, andoxygen atoms, the framework further comprising a plurality of microporesand a plurality of mesopores, the fibrous hierarchical zeolite beingfunctionalized with at least one terminal hydroxyl. The nanoparticlescomprising platinum are immobilized on the framework.

Additional features and advantages of the described embodiments will beset forth in the detailed description, which follows, and in part willbe readily apparent to those skilled in the art from that description orrecognized by practicing the described embodiments, including thedetailed description which follows, the claims, as well as the appendeddrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The following detailed description of specific embodiments of thepresent disclosure can be best understood when read in conjunction withthe following drawings, where like structure is indicated with likereference numerals and in which:

FIG. 1 provides an exemplary reaction scheme to produce theplatinum-nanoparticle functionalized zeolite;

FIG. 2 provides the magic angle spinning ¹H solid state Nuclear MagneticResonance (NMR) spectrum of a platinum-containing organometallicfunctionalized ZSM-5 zeolite;

FIG. 3 provides the cross polarization magic angle spinning ¹³C solidstate Nuclear Magnetic Resonance (NMR) spectrum of a platinum-containingorganometallic functionalized ZSM-5 zeolite;

FIG. 4 provides the magic angle spinning ²⁷Al solid state NuclearMagnetic Resonance (NMR) spectrum of a platinum-containingorganometallic functionalized ZSM-5 zeolite;

FIG. 5 provides the X-ray photoelectron spectroscopy of aplatinum-nanoparticle functionalized ZSM-5 zeolite;

FIG. 6 provides the X-ray photoelectron spectroscopy of aplatinum-nanoparticle functionalized ZSM-5 zeolite;

FIG. 7 provides scanning transmission electron microscopy images of aplatinum-nanoparticle functionalized ZSM-5 zeolite; and

FIG. 8 provides transmission electron microscopy images of aplatinum-nanoparticle functionalized ZSM-5 zeolite.

FIG. 9 provides the particle size distribution of theplatinum-nanoparticles present on a platinum-nanoparticle functionalizedZSM-5 zeolite.

Reference will now be made in greater detail to various embodiments,some embodiments of which are illustrated in the accompanying drawings.Whenever possible, the same reference numerals will be used throughoutthe drawings to refer to the same or similar parts.

DETAILED DESCRIPTION

The present disclosure is directed to zeolites that are modified by theinclusion of platinum nanoparticle functionalization. According toembodiments disclosed herein, the functionalized zeolites may be formedby a process that includes dehydroxylating an initial zeolite, forming aplatinum organometallic complex functionalized zeolite from thedehydroxylated zeolite, and forming the platinum nanoparticlefunctionalized zeolite from the platinum organometallic complexfunctionalized zeolite. While embodiments of functionalized zeolitesprepared by this procedure are disclosed herein, embodiments of thepresent disclosure should not be considered to be limited to zeolitesmade by such a process.

As presently described, “initial” zeolites (which in some embodimentsmay be hierarchical mesoporous zeolites) may be supplied or produced, asis presently disclosed. As described herein, the characterization of thestructure and material of the zeolite may apply to the initial zeoliteas well as the dehydroxylated zeolite and/or the functionalized zeolite.In one or more embodiments, the structure and material composition ofthe initial zeolite does not substantially change through thedehydroxylation and/or functionalization steps (aside from the describedfunctionalities formed by the dehydroxylation and/or platinumnanoparticle functionalization steps). For example, the framework typeand general material constituents of the framework may be substantiallythe same in the initial zeolite and the functionalized zeolite asidefrom the addition of the platinum nanoparticles. Additionally, themesoporosity of the initial zeolite may be carried into thefunctionalized zeolite. Accordingly, when a “zeolite” is describedherein with respect to its structural characterization, the descriptionmay refer to the initial zeolite, the dehydroxylated zeolite, and/or theplatinum nanoparticle functionalized zeolite.

As used throughout this disclosure, “zeolites” may refer tomicropore-containing inorganic materials with regular intra-crystallinecavities and channels of molecular dimension. Zeolites generallycomprise a crystalline structure, as opposed to an amorphous structuresuch as what may be observed in some porous materials such as amorphoussilica. Zeolites generally include a microporous framework which may beidentified by a framework type. The microporous structure of zeolites(e.g., 0.3 nm to 2 nm pore size) may render large surface areas anddesirable size-/shape-selectivity, which may be advantageous forcatalysis. The zeolites described may include, for example,aluminosilicates, titanosilicates, or pure silicates. In embodiments,the zeolites described may include micropores (present in themicrostructure of a zeolite), and additionally include mesopores. Asused throughout this disclosure, micropores refer to pores in astructure that have a diameter of greater than or equal to 0.1 nm andless than or equal to 2 nm, and mesopores refer to pores in a structurethat have a diameter of greater than 2 nm and less than or equal to 50nm. Unless otherwise described herein, the “pore size” of a materialrefers to the average pore size, but materials may additionally includemicropores and/or mesopores having a particular size that is notidentical to the average pore size.

Generally, zeolites may be characterized by a framework type whichdefines their microporous structure. The zeolites described presently,in one or more embodiments, are not particularly limited by frameworktype. Framework types are described in, for example, “Atlas of ZeoliteFramework Types” by Ch. Baerlocher et al, Fifth Revised Edition, 2001,which is incorporated by reference herein. In embodiments, the zeolitesmay comprise microstructures (which include micropores) characterizedas, among others, *BEA framework type zeolites (such as, but not limitedto, zeolite Beta), FAU framework type zeolites (such as, but not limitedto, zeolite Y), MOR framework type zeolites, or MFI framework typezeolite (such as, but not limited to, ZSM-5). It should be understoodthat *BEA, MFI, MOR, and FAU refer to zeolite framework types asidentified by their respective three letter codes established by theInternational Zeolite Association (IZA). Other framework types arecontemplated in the presently disclosed embodiments.

In one or more embodiments, the zeolite may comprise an aluminosilicatemicrostructure. The zeolite may comprise at least 99 wt.% of thecombination of silicon atoms, oxygen atoms, and aluminum atoms. Themolar ratio of Si/Al may be from 2 to 100, such as from 2 to 25, from 25to 50, from 30 to 50, from 50 to 75, from 75 to 100, or any combinationof these ranges.

In one or more embodiments, the zeolite may be an MFI framework typezeolite, such as a ZSM-5. “ZSM-5” generally refers to zeolites having anMFI framework type according to the IZA zeolite nomenclature andcomprising mostly silica and alumina, as is understood by those skilledin the art. ZSM-5 refers to “Zeolite Socony Mobil-5” and is a pentasilfamily zeolite that can be represented by the chemical formulaNa_(n)Al_(n)Si₉₆-nO₁₉₂‧16H₂O, where 0<n<27. According to one or moreembodiments, the molar ratio of silica to alumina in the ZSM-5 may be atleast 5. For example, the molar ratio of silica to alumina in the ZSM-5zeolite may be at least 10, at least 12, or even at least 30, such asfrom 5 to 30, from 12 to 30, from 5 to 80, from 5 to 300, from 5 to1000, or even from 5 to 1500. Examples of suitable ZSM-5 zeolite includethose commercially available from Zeolyst International, such asCBV2314, CBV3024E, CBV5524G, and CBV28014, and from TOSOH Corporation,such as HSZ-890 and HSZ-891.

In one or more embodiments, the zeolite may comprise an FAU frameworktype zeolite, such as zeolite Y or ultra-stable zeolite Y (USY). As usedherein, “zeolite Y” and “USY” refer to a zeolite having a FAU frameworktype according to the IZA zeolite nomenclature and comprising mostlysilica and alumina, as would be understood by one skilled in the art. Inone or more embodiments, USY may be prepared from zeolite Y by steamingzeolite Y at temperatures above 500° C. The molar ratio of silica toalumina may be at least 3. For example, the molar ratio of silica toalumina in the zeolite Y may be at least 5, at least 12, at least 30, oreven at least 200, such as from 5 to 200, from 12 to 200, or from about15 to about 200. The unit cell size of the zeolite Y may be from about24 Angstrom to about 25 Angstrom, such as 24.56 Angstrom.

In one or more embodiments, the zeolite may comprise a *BEA frameworktype zeolite, such as zeolite Beta. As used in this disclosure, “zeoliteBeta” refers to a zeolite having a *BEA framework type according to theIZA zeolite nomenclature and comprising mostly silica and alumina, aswould be understood by one skilled in the art. The molar ratio of silicato alumina in the zeolite Beta may be at least 10, at least 25, or evenat least 100. For example, the molar ratio of silica to alumina in thezeolite Beta may be from 5 to 500, such as from 25 to 300.

In embodiments, the initial zeolites may include well-defined isolatedsilanol groups and not completely lose Bronsted acid sites upondehydroxylation at high temperatures.

Along with micropores, which may generally define the framework type ofthe zeolite, the zeolites may also comprise mesopores. As a result ofhaving more than one type of pore, the zeolites used in certainembodiments herein may be referred to as “hierarchical zeolites.” Asused herein a “mesoporous zeolite” refers to a zeolite which includesmesopores, and may have an average pore size of from 2 to 50 nm. Thepresently disclosed hierarchical zeolites may have an average pore sizeof greater than 2 nm, such as from 4 nm to 16 nm, from 6 nm to 14 nm,from 8 nm to 12 nm, or from 9 nm to 11 nm. In some embodiments, themajority of the mesopores may be greater than 8 nm, greater than 9 nm,or even greater than 10 nm. The mesopores of the hierarchical zeolitesdescribed may range from 2 nm to 40 nm, and the median pore size may befrom 8 nm to 12 nm. In embodiments, the mesopore structure of thezeolites may be fibrous, where the mesopores are channel-like. Asdescribed herein, “fibrous zeolites” may comprise reticulate fibers withinterconnections and have a dense inner core surrounded by less denseouter fibers. Generally, fibrous zeolites may comprise intercrystallinevoids between the fibers where the voids between the less dense, outerfibers are mesopore sized and give the fibrous zeolite its mesoporosity.The hierarchical zeolites described may be generally silica-containingmaterials, such as aluminosilicates, pure silicates, or titanosilicates.It should be understood that while hierarchical zeolites are referencedin one or more portions of the present disclosure, some zeolites may notbe mesoporous. For example, some embodiments may utilize zeolites whichhave an average pore size of less than 2 nm, or may not have mesoporesin any capacity.

The hierarchical zeolites described in the present disclosure may haveenhanced catalytic activity as compared to non-mesoporous zeolites.Without being bound by theory, it is believed that the microporousstructures provide for the majority of the catalytic functionality ofthe hierarchical zeolites described. The mesoporosity may additionallyallow for greater catalytic functionality because more micropores areavailable for contact with the reactant in a catalytic reaction. Themesopores generally allow for better access to microporous catalyticsites on the hierarchical zeolite, especially when reactant moleculesare relatively large. For example, larger molecules may be able todiffuse into the mesopores to contact additional catalytic microporoussites. Additionally, mesoporosity may allow for additional graftingsites on the zeolite where organometallic moieties may be bound.

In embodiments, the hierarchical zeolites may have a surface area ofgreater than or equal to 300 m2/g, greater than or equal to 350 m2/g,greater than or equal to 400 m2/g, greater than or equal to 450 m2/g,greater than or equal to 500 m2/g, greater than or equal to 550 m2/g,greater than or equal to 600 m2/g, greater than or equal to 650 m2/g, oreven greater than or equal to 700 m2/g, and less than or equal to 1,000m2/g. In one or more other embodiments, the hierarchical zeolites mayhave pore volume of greater than or equal to 0.2 cm³/g, greater than orequal to 0.25 cm³/g, greater than or equal to 0.3 cm³/g, greater than orequal to 0.35 cm³/g, greater than or equal to 0.4 cm³/g, greater than orequal to 0.45 cm³/g, greater than or equal to 0.5 cm³/g, greater than orequal to 0.55 cm³/g, greater than or equal to 0.6 cm³/g, greater than orequal to 0.65 cm³/g, or even greater than or equal to 0.7 cm³/g, andless than or equal to 1.5 cm³/g. In further embodiments, the portion ofthe surface area contributed by mesopores may be greater than or equalto 20%, greater than or equal to 25%, greater than or equal to 30%,greater than or equal to 35%, greater than or equal to 40%, greater thanor equal to 45%, greater than or equal to 50%, greater than or equal to55%, greater than or equal to 60%, or even greater than or equal to 65%,such as between 20% and 70% of total surface area. In additionalembodiments, the portion of the pore volume contributed by mesopores maybe greater than or equal to 20%, greater than or equal to 30%, greaterthan or equal to 35%, greater than or equal to 40%, greater than orequal to 45%, greater than or equal to 50%, greater than or equal to55%, greater than or equal to 60%, greater than or equal to 65%, greaterthan or equal to 70%, or even greater than or equal to 75%, such asbetween 20% and 80% of total pore volume. Surface area, average poresize, and pore volume distribution may be measured by N₂ adsorptionisotherms performed at 77 Kelvin (K) (such as with a Micrometrics ASAP2020 system). As would be understood by those skilled in the art,Brunauer-Emmett-Teller (BET) analysis methods may be utilized.

The hierarchical zeolites described may form as particles that may begenerally spherical in shape or irregular globular shaped (that is,non-spherical). In embodiments, the particles have a “particle size”measured as the greatest distance between two points located on a singlezeolite particle. For example, the particle size of a spherical particlewould be its diameter. In other shapes, the particle size is measured asthe distance between the two most distant points of the same particlewhen viewed in a microscope, where these points may lie on outersurfaces of the particle. The particles may have a particle size from 25nm to 900 nm, from 25 nm to 800 nm, from 25 nm to 700 nm, from 25 nm to600 nm, from 25 nm to 500 nm, from 50 nm to 400 nm, from 100 nm to 300nm, or less than 900 nm, less than 800 nm, less than 700 nm, less than600 nm, less than 500 nm, less than 400 nm, less than 300 nm, or lessthan 250 nm. Particle sizes may be determined by visual examinationunder a microscope.

The hierarchical zeolites described may be formed in a single-crystalstructure, or if not single crystal, may be comprised of a limitednumber of crystals, such as 2, 3, 4, or 5. The crystalline structure ofthe hierarchical zeolites may have a branched, fibrous structure withhighly interconnected intra-crystalline mesopores. Such structures maybe advantageous in applications where the structural integrity of thezeolite is important while the ordering of the mesopores is not.

According to one or more embodiments, the hierarchical zeolitesdescribed in the present disclosure may be produced by utilizingcationic polymers, as is subsequently described in the presentdisclosure, as structure-directing agents. The cationic polymers mayfunction as dual-function templates for synthesizing the hierarchicalzeolites, meaning that they act simultaneously as a template for thefabrication of the micropores and as a template for the fabrication ofthe mesopores.

According to various embodiments, the hierarchical zeolites described inthe present disclosure may be produced by forming a mixture comprisingthe cationic polymer structure-directing agent (SDA), such aspoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-tripropylhexane-1,6-diamoniumbromide), referred to as (PDAMAB-TPHAB) and shown in formula (1), andone or more precursor materials, which will form the structure of thehierarchical zeolites. The precursor materials may contain the materialsthat form the porous structures, such as alumina and silica for analuminosilicate zeolite, titania and silica for a titanosilicatezeolite, and silica for a pure silica zeolite. For example, theprecursor materials may be one or more of a silicon-containing material,a titanium-containing material, and an aluminum-containing material. Forexample, at least NaAlO₂, tetraethylorthosilicate, and the cationicpolymer may be mixed in an aqueous solution to form an intermediatematerial that will become a mesoporous aluminosilicate zeolite. Itshould be appreciated that other precursor materials that includesilica, titania, or alumina may be utilized. For example, in otherembodiments, tetraethylorthosilicate and cationic polymers may becombined to form an intermediate material that will become a silicatehierarchical zeolite; or tetraethylorthosilicate,tetrabutylorthotitanate, and cationic polymer may be combined to form anintermediate material that will become a titanosilicate hierarchicalzeolite. Optionally, the combined mixture may be heated to form theintermediate material, and may crystallize under autoclave conditions.The intermediate material may comprise micropores, and the cationicpolymer may act as a structure-directing agent in the formation of themicropores during crystallization. The intermediate materials may stillcontain the cationic polymers which may at least partially define thespace of the mesopores following their removal. The products may becentrifuged, washed, and dried, and finally, the polymer may be removedby a calcination step. The calcination step may comprise heating attemperatures of at least about 400° C., 500° C., 550° C., or evengreater. Without being bound by theory, it is believed that the removalof the polymers forms at least a portion of the mesopores of thehierarchical zeolite, where the mesopores are present in the space onceinhabited by the polymers.

The precursor materials of the mixture, or reagents of the sol-gel,generally determine the material composition of the hierarchicalzeolites, such as an aluminosilicate, a titanosilicate, or a puresilicate. An aluminosilicate hierarchical zeolite may comprise a molarratio of Si/Al of from 2 to 10,000, from 25 to 10,000, from 50 to10,000, from 100 to 10,000, from 200 to 10,000, from 500 to 10,000, from1,000 to 10,000, or even from 2,000 to 10,000. In a pure silicatezeolite, a negligible amount or no amount of aluminum is present in theframework of the zeolite, and the Si/Al molar ratio theoreticallyapproaches infinity. As used herein a “pure silicate” refers to amaterial comprising at least about 99.9 weight percent (wt.%) of siliconand oxygen atoms in the framework of the zeolite. Other materials,including water and sodium hydroxide, may be utilized during theformation of the material but are not present in the framework of thezeolite. A pure silica hierarchical zeolite may be formed by utilizingonly silicon-containing materials to form the framework of the zeoliteand no aluminum. A titanosilicate porous structure may comprise a molarratio of Si/Ti of from 30 to 10,000, from 40 to 10,000, from 50 to10,000, from 100 to 10,000, from 200 to 10,000, from 500 to 10,000, from1,000 to 10,000, or even from 2,000 to 10,000. It has been found thatPDAMAB-TPHAB cationic polymer, described herein, may be utilized to formmesoporous ZSM-5 zeolites when used with silica and alumina precursormaterials, mesoporous TS-1 zeolites when used with a silica and titaniaprecursor, and mesoporous silicalite-I zeolites when used with silicaprecursors. It has also been found that PDAMAB-TMHAB may be utilized toform mesoporous Beta zeolites when used with silica and aluminaprecursors.

The cationic polymers presently disclosed may comprise one or moremonomers which each comprise multiple cationic functional groups, suchas quaternary ammonium cations or quaternary phosphonium cations. Thecation functional groups of the monomers may be connected by ahydrocarbon chain. Without being bound by theory, it is believed thatthe cationic functional groups may form or at least partially aid informing the microstructure of the hierarchical zeolite (for example, anMFI framework type or BEA framework type) and the hydrocarbon chains andother hydrocarbon functional groups of the polymer may form or at leastpartially aid in forming the mesopores of the hierarchical zeolite.

The cationic polymers may comprise functional groups, which are utilizedas SDAs for the fabrication of the zeolite microstructure. Suchfunctional groups, which are believed to form the zeolitemicrostructure, include quaternary ammonium cations and quaternaryphosphonium cations. Quaternary ammonium is generally depicted informula (2) and quaternary phosphonium is generally depicted in formula(3).

As used throughout this disclosure, the encircled plus symbols (“+”)show cationic positively charged centers. One or more of the various Rgroups may be structurally identical or may be structurally differentfrom one another. In formula (2) and formula (3), R₁, R₂, R₃, and R₄ mayinclude hydrogen atoms or hydrocarbons, such as a hydrocarbon chain,optionally comprising one or more heteroatoms. As used throughout thisdisclosure, a “hydrocarbon” refers to a chemical or chemical moietycomprising hydrogen and carbon. For example, the hydrocarbon chain maybe branched or unbranched, and may comprise an alkane hydrocarbon chain,an alkene hydrocarbon chain, or an alkyne hydrocarbon chain, includingcyclic or aromatic moieties. In some embodiments, one or more of R₁, R₂,R₃, and R₄ may represent hydrogen atoms. As used throughout thisdisclosure, a heteroatom is a non-carbon and non-hydrogen atom. Inembodiments, quaternary ammonium and quaternary phosphonium may bepresent in a cyclic moiety, such as a five-atom ring, a six-atom ring,or a ring comprising a different number of atoms. For example, informula (2) and formula (3), the R₁ and R₂ constituents may be part ofthe same cyclic moiety.

In one or more embodiments, the two cation moieties may form ionic bondswith anions. Various anionic chemical species are contemplated,including Cl⁻, Br⁻, F⁻, I⁻, ⁻OH, ½SO₄ ²⁻, ¹/₃PO₄ ³⁻, ½S²⁻, AlO₂ ⁻, BF₄⁻, SbF₆ ⁻, and B[3,5-(CF₃)₂C₆H₃]₄ ⁻ (commonly referred to as “BArF”). Insome embodiments, an anion with a negative charge of more than 1⁻, suchas 2⁻, 3⁻, or 4⁻, may be utilized, and in those embodiments, a singleanion may pair with multiple cations of the cationic polymer. As usedthroughout this disclosure, a fraction listed before an anioniccomposition means that the anion is paired with more than one cation andmay, for example, be paired with the number of cations equal to itsnegative charge.

In one or more embodiments, a hydrocarbon chain may separate two cationsof a monomer from one another. As described above, the hydrocarbon chainmay be branched or unbranched, and may comprise an alkane hydrocarbonchain, an alkene hydrocarbon chain, or an alkyne hydrocarbon chain,including cyclic or aromatic moieties. In one embodiment, the length ofthe hydrocarbon chain (measured as the number of carbons in the chaindirectly connecting the two cations) may be from 1 to 10,000 carbonatoms, such 1 to 20 carbon atom alkane chains.

The cationic polymers described in this disclosure are generallynon-surfactants. A surfactant refers to a compound that lowers thesurface tension (or interfacial tension) between two liquids or betweena liquid and a solid, usually by the inclusion of a hydrophilic head anda hydrophobic tail. Non-surfactants do not contain such hydrophobic andhydrophilic regions, and do not form micelles in a mixture containing apolar material and non-polar material. Without being bound by theory, itis believed that the polymers described are non-surfactants because ofthe inclusion of two or more cation moieties, which are joined by ahydrocarbon chain. Such an arrangement has polar charges on or near eachend of the monomer, and such an arrangement excludes the hydrophobicsegment from the polymer, and thus limits the surfactant behavior(self-assembly in solution). On the atomic scale, it is believed thatthe functional groups (for example, quaternary ammoniums) on the polymerdirect the formation of zeolite structure; on the mesoscale, the polymerfunctions simply as a “porogen” rather than a structure directing agentin the conventional sense. As opposed to the cases of surfactants,non-surfactant polymers do not self-assemble to form an orderedmeso-structure, which in turn favors the crystallization of zeolites,producing a new class of hierarchical zeolites that featurethree-dimensionally (3-D) continuous zeolitic frameworks with highlyinterconnected intracrystalline mesopores.

In one embodiment, the cationic polymer may comprise the generalizedstructure depicted in formula (4):

Formula (4) depicts a single monomer of the cationic polymer, which issignified by the included bracket, where n is the total number ofrepeating monomers in the polymer. In some embodiments, the cationicpolymer may be a copolymer comprising two or more monomer structures.The X and Y of formula (4) independently represent anions, such as Cl⁻,Br⁻, F⁻, I⁻, ⁻OH, ½SO₄ ²⁻, ¹/₃PO₄ ³⁻, ½S²⁻, AlO₂ ⁻, BF₄ ⁻ , SbF₆ ⁻, andB[3,5-(CF₃)₂C₆H₃]⁴ ⁻. In some embodiments, an anion with a negativecharge of more than 1⁻, such as 2⁻, 3⁻, or 4⁻, may be utilized, and inthose embodiments, a single anion may pair with multiple cations of thecationic polymer of formula (4). It should be understood that one ormore monomers (such as that shown in formula (4)) of the cationicpolymers described in the present application may be different from oneanother. For example, various monomer units may include different Rgroups. Referring to formula (4), A and B may independently representnitrogen or phosphorus. In one embodiment, A and B may both be nitrogen.In one embodiment, A may be nitrogen and B may be phosphorus. In oneembodiment, A may be phosphorus and B may be nitrogen. In anotherembodiment, A and B may both be phosphorus. For example, A may comprisea quaternary ammonium cation or a quaternary phosphonium cation, and Bmay comprise a quaternary ammonium cation or a quaternary phosphoniumcation. As shown in formula (4), A may be a portion of a ring structure,such as a five-membered ring. R₅ may be a branched or unbranchedhydrocarbon chain, optionally further including at least one heteroatom,having a carbon chain length of from 1 to 10,000 carbon atoms, such as a2 to 20 carbon alkane, and R₆, R₇, R₈, R₉, Rio, R₁₁, R₁₂, and R₁₃ mayindependently be a hydrogen atom or a hydrocarbon optionally comprisingone or more heteroatoms. For example, one or more of R₆, R₇, R₈, R₉,Rio, R₁₁, R₁₂, and R₁₃ may independently be hydrogen or an alkyl group,such as a methyl group, an ethyl group, a propyl group, a butyl group,or a pentyl group. In embodiments, one or more of R₆, R₇, R₈, and R₉ maybe hydrogen. In embodiments, one or more of Rio, R₁₁, R₁₂, and R₁₃ maybe the same or different and may be an alkyl group. For example, R₁₀ maybe a methyl, an ethyl, a propyl, or a butyl group, and one or more ofR₁₁, R₁₂, and R₁₃ may independently be a methyl, an ethyl, a propyl, ora butyl group. In one embodiment, R₁₀ is a methyl group and R₁₁, R₁₂,and R₁₃ are all propyl groups. In one embodiment, R₁₁, R₁₂, and R₁₃ areall methyl groups. In another embodiment, R₁₁, R₁₂, and R₁₃ are allethyl groups. In another embodiment, R₁₁, R₁₂, and R₁₃ are all propylgroups.

In one or more embodiments, formula (4) may be a polymer that comprisesn monomer units, where n may be from 10 to 10,000,000, such as from 50to 10,000,000, from 100 to 10,000,000, from 250 to 10,000,000, from 500to 10,000,000, from 1,000 to 10,000,000, from 5,000 to 10,000,000, from10,000 to 10,000,000, from 100,000 to10,000,000, from 1,000,000 to10,000,000, from 10 to 1,000,000, from 10 to 100,000, from 10 to 10,000,from 10 to 5,000, from 10 to 1,000, from 10 to 500, from 10 to 250, orfrom 10 to 100. For example, n may be from 1,000 to 1,000,000.

According to one or more embodiments, the cationic polymer comprisespoly(N¹,N¹-diallyl-N¹-alkyl-N⁶,N⁶,N⁶-trialkylalkane-1,6-diamoniumhalide), such aspoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-trialkylhexane-1,6-diamoniumbromide). An example of such is PDAMAB-TPHAB, as shown in formula (1).

In another embodiment, the cationic polymer comprisespoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-triethylhexane-1,6-diamoniumbromide), referred to as (PDAMAB-TEHAB) and shown in formula (5).

In another embodiment, the cationic polymerpoly(N¹,N¹-diallyl-N¹-methyl-N⁶,N⁶,N⁶-trimethylhexane-1,6-diamoniumbromide) is referred to as (PDAMAB-TMHAB) and is shown in formula (6).

Other cationic polymers, including co-polymers, capable of acting ascationic polymer structure-directing agents have been disclosedpreviously. It is envisioned that such cationic polymerstructure-directing agents could be used in the synthesis of thezeolites described herein.

According to one or more embodiments disclosed herein, either of thezeolites described above, hierarchical zeolites or conventionalnon-mesoporous zeolites, may serve as an “initial zeolite” which is thendehydroxylated, forming a dehydroxylated zeolite. In general, theinitial zeolite may refer to a zeolite, which is not substantiallydehydroxylated and includes at least a majority of vicinal hydroxylgroups. Dehydroxylation, as is commonly understood by those skilled inart, involves a reaction whereby a water molecule is formed by therelease of a hydroxyl group and its combination with a proton. Asdescribed herein, a “dehydroxylated zeolite” refers to a zeoliticmaterial that has been at least partially dehydroxylated (i.e., H and Oatoms are liberated from the initial zeolite and water is formed).Without being bound by theory, it is believed that the dehydroxylationreaction forms a molecule of water from a hydroxyl group of a firstsilanol and a hydrogen of a second silanol of a zeolite. The remainingoxygen atom of the second silanol functionality forms a siloxane groupin the zeolite (i.e., (═Si—O—Si), sometimes referred to as a strainedsiloxane bridge. These strained siloxane bridges may be reactive insubsequent functionalization steps, as is described herein. Generally,strained siloxane bridges are those formed in the dehydroxylationreaction and not in the formation of the initial zeolite. The initialzeolite may primarily comprise vicinal silanol functionalities. In oneor more embodiments, dehydroxylating the initial zeolite may formisolated terminal silanol functionalities comprising hydroxyl groupsbonded to silicon atoms of the microporous framework of thedehydroxylated zeolite.

As described herein “silanol functionalities” refer to ═Si—O—H groups.Silanol groups generally include a silicon atom and a hydroxyl group(-OH). As described herein, “terminal” functionalities refer to thosethat are bonded to only one other atom. For example, the silanolfunctionality may be terminal by being bonded to only one other atomsuch as a silicon atom of the microporous framework. As describedherein, “isolated silanol functionalities” refer to silanolfunctionalities that are sufficiently distant from one another such thathydrogen-bonding interactions are avoided with other silanolfunctionalities. These isolated silanol functionalities are generallysilanol functionalities on the zeolite that are non-adjacent to othersilanol functionalities. Generally, in a zeolite that includes siliconand oxygen atoms, “adjacent silanols” are those that are directly bondedthrough a bridging oxygen atom. Those skilled in the art wouldunderstand isolated silanol functionalities may be identified by FT-IRand/or ¹H-NMR. For example, isolated silanol functionalities may becharacterized by a sharp and intense FT-IR band at about 3749 cm⁻¹and/or a ¹H-NMR shift at about 1.8 ppm. In the embodiments describedherein, peaks at or near 3749 cm⁻¹ in FT-IR and/or at or near 1.8 ppm in¹H-NMR may signify the existence of the dehydroxylated zeolite, and thelack of peaks at or near these values may signify the existence of theinitial zeolite.

Isolated silanol functionalities can be contrasted with vicinal silanolfunctionalities, where two silanol functionalities are “adjacent” oneanother by each being bonded with a bridging oxygen atom. Formula (7)depicts an isolated silanol functionality and formula (8) depicts avicinal silanol functionality. Hydrogen bonding occurs between theoxygen atom of one silanol functionality and the hydrogen atom of anadjacent silanol functionality in the vicinal silanol functionality.Vicinal silanol functionality may show a different band in FT-IR and adifferent ¹H-NMR shift, such as 3520 cm⁻¹ or 3720 cm⁻¹ in FT-IR, and 2.7ppm in ¹H-NMR. It should be understood that, according to one or moreembodiments presently disclosed, the various functional groups of thezeolites may be identified by FT-IR and/or ¹H-NMR methods. When azeolite “comprises” such a moiety, such inclusion may be evidenced by apeak at or near the bands in FT-IR and/or ¹H-NMR corresponding to suchmoiety. Those skilled in the art would understand such detectionmethods.

In one or more embodiments, the initial zeolite (as well as thedehydroxylated zeolite) comprises aluminum in addition to silicon andoxygen. For example, ZSM-5 zeolite may include such atoms. Inembodiments with aluminum present, the microporous framework of thedehydroxylated zeolite may include Bronsted acid silanolfunctionalities. In the Bronsted acid silanol functionalities, eachoxygen atom of the Bronsted acid silanol functionality may bridge asilicon atom and an aluminum atom of the microporous framework. SuchBronsted acid silanol functionalities may be expressed as[≡Si—O(H)➜Al≡]. In this representation, a dative bond from oxygen atomelectron lone pairs to the aluminum atom is shown by the arrow. Formula(9) depicts an example of an aluminosilicate zeolite framework structurethat includes the isolated terminal silanol functionalities and Bronstedacid silanol functionalities described herein.

According to one or more embodiments, the dehydroxylation of the initialzeolite may be performed by heating the initial zeolite at elevatedtemperatures under vacuum, such as from 700° C. to 1100° C. According toembodiments, the temperature of heating may be from 600° C. to 650° C.,from 650° C. to 700° C., from 700° C. to 750° C., from 750° C. to 800°C., from 800° C. to 850° C., from 850° C. to 900° C., from 900° C. to950° C., from 950° C. to 1000° C., from 1000° C. to 1050° C., from 1050°C. to 1100° C., or any combination of these ranges. For example,temperature ranges from 650° C. to any named value are contemplated, andtemperature ranges from any named value to 1100° C. are contemplated. Asdescribed herein, vacuum pressure refers to any pressure less thanatmospheric pressure. According to some embodiments, the pressure duringthe heating process may be less than or equal to 10⁻² mbar, less than orequal to 10⁻²⁵ mbar, less than or equal to 10⁻³ mbar, less than or equalto 10⁻³⁵ mbar, less than or equal to 10⁻⁴ mbar, or even less than orequal to 10⁻⁴ \-⁵ mbar. The heating times may be sufficiently long suchthat the zeolite is brought to thermal equilibrium with the oven orother thermal apparatus utilized. For example, heating times of greaterthan or equal to 8 hours, greater than or equal to 12 hours, or greaterthan or equal to 18 hours may be utilized. For example, about 24 hoursof heating time may be utilized.

It is believed that according to one or more embodiments describedherein, heating at temperatures below 600° C. may be insufficient toform terminal isolated silanol functionalities. However, heating attemperatures greater than 1100° C. may result in the elimination ofterminal isolated silanol functionalities, or the production of suchfunctionalities in low enough concentrations that further processing bycontact with organometallic chemicals to form organometallicfunctionalities is not observed, as is described subsequently herein.Without being bound by any particular theory, it is believed thatgreater heating temperatures during dehydroxylation correlate withreduced terminal silanols present on the dehydroxylated zeolite.However, it is believed that greater heating temperatures duringdehydroxylation correlate with greater amounts of strained siloxanes.For example, when the initial zeolite is heated at 700° C. duringdehydroxylation, the concentration of isolated terminal silanol groupsmay be at least 0.4 mmol/g, such as approximately 0.45 mmol/g in someembodiments, as measured by methyl lithium titration. Dehydroxylating at1100° C. may result in much less isolated terminal silanol and/or muchless isolated Bronsted acid silanol. In some embodiments, less than 10%of the isolated terminal silanol groups present at 700° C.dehydroxylation are present when 1100° C. dehydroxylation heating isused. However, it is believed that strained siloxane groups areappreciably greater at these greater dehydroxylation temperatures.

In one or more embodiments, the dehydroxylated zeolite may be processedto form the platinum nanoparticle functionalized zeolite. Generally, toform the platinum nanoparticle functionalized zeolite, an organometalliccomplex comprising a platinum atom may be contacted and/or reacted withthe dehydroxylated zeolite, thereby producing a functionalized zeolitecomprising isolated terminal organometallic functionalities comprising aplatinum atom. The thus functionalized zeolite may then be reacted withan atmosphere comprising H₂, thereby forming the platinum nanoparticlefunctionalized zeolite. Exemplary organometallic complexes comprising aplatinum atom include, but are not limited to, complexes of formulae10-18 and mixtures of two or more thereof.

An exemplary reaction scheme to produce the platinum-nanoparticlefunctionalized zeolite from the dehydroxylated zeolite is shown in FIG.1 . In particular, the isolated terminal hydroxyl functionalities of thezeolite of formula (19) may be reacted with a platinum-containingorganometallic compound, such as the platinum organometallic complex offormula (10) as shown, producing methane as a by-product. That is, inaddition to the functionalized zeolite comprising isolated terminalorganometallic functionalities comprising a platinum atom, such as thefunctionalized zeolite of formula (20), methane is also produced whenthe platinum-containing organometallic compound is a complex of formula(10). The functionalized zeolite comprising isolated terminalorganometallic functionalities (20) may then be contacted with H₂ toproduce the platinum-nanoparticle functionalized zeolite of formula(21). Additionally, in embodiments where aluminum is present in thezeolitic framework structure and Bronsted acid oxygens are present inthe dehydroxylated zeolite, platinum nanoparticles may be associatedwith the zeolite framework in a manner that allows lone electron pairsof an oxygen atom to form a coordinate bond with a nearby aluminum atom.

In embodiments, the formation of the functionalized zeolite comprisingisolated terminal organometallic functionalities comprising a platinumatom from the dehydroxylated zeolite may be conducted at a temperaturefrom 15° C. to 30° C., from 16° C. to 30° C., from 17° C. to 30° C.,from 18° C. to 30° C., from 19° C. to 30° C., from 20° C. to 30° C.,from 21° C. to 30° C., from 22° C. to 30° C., from 23° C. to 30° C.,from 24° C. to 30° C., from 25° C. to 30° C., from 15° C. to 29° C.,from 15° C. to 28° C., from 15° C. to 27° C., from 15° C. to 26° C.,from 15° C. to 25° C., from 15° C. to 24° C., from 15° C. to 23° C.,from 15° C. to 22° C., from 15° C. to 21° C., or even from 15° C. to 20°C. In embodiments, the reaction may be conducted at a temperaturetypically referred to as “room temperature.” That is, in embodiments,the reaction may be conduct at about 20° C. or 20 ± 4° C.

In embodiments, the dehydroxylated zeolite may be allowed to react withthe platinum-containing organometallic complex for from 5 hours to 25hours, from 6 hours to 25 hours, from 7 hours to 25 hours, from 8 hoursto 25 hours, from 9 hours to 25 hours, from 10 hours to 25 hours, from11 hours to 25 hours, from 12 hours to 25 hours, from 13 hours to 25hours, from 14 hours to 25 hours, from 16 hours to 25 hours, from 17hours to 25 hours, from 18 hours to 25 hours, from 19 hours to 25 hours,from 20 hours to 25 hours, from 5 hours to 24 hours, from 5 hours to 23hours, from 5 hours to 22 hours, from 5 hours to 21 hours, from 5 hoursto 20 hours, from 5 hours to 19 hours, from 5 hours to 18 hours, from 5hours to 17 hours, from 5 hours to 16 hours, from 5 hours to 15 hours,from 5 hours to 14 hours, from 5 hours to 13 hours, from 5 hours to 12hours, from 5 hours to 11 hours, or even from 5 hours to 10 hours. Inembodiments, the dehydroxylated zeolite may be allowed to react with theplatinum-containing organometallic complex for about 6 hours or 6 ± 1hours.

It is envisioned that, in various embodiments, the dehydroxylatedzeolite may be allowed to react with the platinum-containingorganometallic complex at any combination of temperature and timedisclosed herein.

Reaction of the dehydroxylated zeolite with the platinum-containingorganometallic complex may take place in a suitable solvent. Selectionof the solvent is within the level of ordinary skill in the art and willbe determined in view of multiple factors, such as solubility of thereactants in the solvent, intended temperature of the reaction, and likeconsiderations. In embodiments, the solvent may be a hydrocarbon solventsuch as pentane, hexane, heptane, octane, benzene, toluene, xylene, andcombinations of two or more thereof. In embodiments, the solventcomprises, consists essentially of, or consists of benzene. Inembodiments, the solvent comprises, consists essentially of, or consistsof pentane. In embodiments, the solvent may be an ethereal solvent suchas diethyl ether, dimethoxy ethane, tetrahydrofuran (THF), dioxane, andcombinations of two or more thereof.

In embodiments, the platinum-containing organometallic functionalizedzeolite may then be contacted with hydrogen gas (H₂). The H₂ may beadded to the platinum-containing organometallic functionalized zeoliteat a pressure from 0.5 atm to 1.5 atm, from 0.6 atm to 1.5 atm, from 0.7atm to 1.5 atm, from 0.8 atm to 1.5 atm, from 0.9 atm to 1.5 atm, from 1atm to 1.5 atm, from 0.5 atm to 1.4 atm, from 0.5 atm to 1.3 atm, from0.5 atm to 1.2 atm, from 0.5 atm to 1.1 atm, or even from 0.5 atm to 1atm. In embodiments, the H₂ partial pressure is about 1 atm or 1 ± 0.2atm. In embodiments, the H₂ may be supplied in an inert carrier gas. Forinstance, the carrier gas may be selected from helium gas, neon gas,argon gas, krypton gas, xenon gas, nitrogen gas, and a combination oftwo or more thereof. Without intending to be bound by theory, it isbelieved that reaction with H₂ reduces the platinum-containingorganometallic functionalities to provide a platinum nanoparticlefunctionalized zeolite.

In embodiments, the reaction with H₂ may be allowed to proceed for from0.5 hours to 3.5 hours, such as from 1 hour to 3 hours, from 1.5 hoursto 2.5 hours, or about 2 ± 0.5 hours. Further, this reaction with H₂ mayproceed at a temperature from 200° C. to 800° C., from 200° C. to 750°C., from 200° C. to 700° C., from 200° C. to 650° C., from 200° C. to600° C., from 200° C. to 550° C., from 200° C. to 500° C., from 200° C.to 450° C., from 200° C. to 400° C., from 200° C. to 350° C., from 200°C. to 300° C., from 200° C. to 250° C., from 250° C. to 800° C., from300° C. to 800° C., from 350° C. to 800° C., from 400° C. to 800° C.,from 450° C. to 800° C., from 450° C. to 650° C., from 500° C. to 800°C., from 525° C. to 575° C., from 550° C. to 800° C., from 600° C. to800° C., from 650° C. to 800° C., from 700° C. to 800° C., or even from750° C. to 800° C.

It is envisioned that, in various embodiments, the platinum-containingorganometallic functionalized zeolite may be allowed to react with theH₂ at any combination of temperature and time disclosed herein.

In one or more embodiments, the amount of platinum grafted onto thefunctionalized zeolite may be quantified by inductively coupled plasmaatomic emission spectroscopy (ICP-AES), also referred to as inductivelycoupled plasma optical emission spectrometry (ICP-OES), which is ananalytical technique used for the detection of chemical elements. Thistype of emission spectroscopy uses inductively coupled plasma to produceexcited atoms and ions that emit electromagnetic radiation atwavelengths characteristic of a particular element. The plasma is a hightemperature source of ionized source gas (often argon). The plasma issustained and maintained by inductive coupling from cooled electricalcoils at megahertz frequencies. The source temperature is in the rangefrom 6000 K to 10,000 K. The intensity of the emissions from variouswavelengths of light is proportional to the concentrations of theelements within the sample.

Generally, the platinum-containing organometallic functionalities may beincorporated onto the framework in a concentration from 0.1 wt% to 10wt%, from 0.5 wt% to 10 wt%, from 0.65 wt% to 10 wt%, from 1 wt% to 10wt%, from 1.5 wt% to 10 wt%, from 2 wt% to 10 wt%, from 2.5 wt% to 10wt%, from 3 wt% to 10 wt%, from 3.5 wt% to 10 wt%, from 4 wt% to 10 wt%,from 4.5 wt% to 10 wt%, from 5 wt% to 10 wt%, 5.5 wt% to 10 wt%, from 6wt% to 10 wt%, from 6.5 wt% to 10 wt%, from 7 wt% to 10 wt%, from 7.5wt% to 10 wt%, from 8 wt% to 10 wt%, from 8.5 wt% to 10 wt%, from 9 wt%to 10 wt%, from 9.5 wt% to 10 wt%, from 0.1 wt% to 9.5 wt%, from 0.1 wt%to 9 wt%, from 0.1 wt% to 8.5 wt%, from 0.1 wt% to 8 wt%, from 0.1 wt%to 7.5 wt%, from 0.1 wt% to 7 wt%, from 0.1 wt% to 6.5 wt%, from 0.1 wt%to 6 wt%, from 0.1 wt% to 5.5 wt%, from 0.1 wt% to 5 wt%, 0.1 wt% to 4.5wt%, from 0.1 wt% to 4 wt%, from 0.1 wt% to 3.5 wt%, from 0.1 wt% to 3wt%, from 0.1 wt% to 2.5 wt%, from 0.1 wt% to 2 wt%, from 0.1 wt% to 1.5wt%, from 0.1 wt% to 1 wt%, from 0.1 wt% to 0.65 wt%, or even from 0.1wt% to 0.5 wt%. In embodiments, the platinum-containing organometallicfunctionalities may be incorporated onto the framework in aconcentration of about 2 wt% or 2 ± 0.4 wt%.

In embodiments, the platinum nanoparticles produced in accordance withthis two-step reaction may have a particle size from 1 nm to 10 nm, from1.5 nm to 10 nm, from 2 nm to 10 nm, from 2.5 nm to 10 nm, from 3 nm to10 nm, from 3.5 nm to 10 nm, from 4 nm to 10 nm, from 4.5 nm to 10 nm,from 5 nm to 10 nm, from 5.5 nm to 10 nm, from 6 nm to 10 nm, from 6.5nm to 10 nm, from 7 nm to 10 nm, from 7.5 nm to 10 nm, from 8 nm to 10nm, from 8.5 nm to 10 nm, from 9 nm to 10 nm, from 9.5 nm to 10 nm, from1 nm to 9.5 nm, from 1 nm to 9 nm, from 1 nm to 8.5 nm, from 1 nm to 8nm, from 1 nm to 7.5 nm, from 1 nm to 7 nm, from 1 nm to 6.5 nm, from 1nm to 6 nm, from 1 nm to 5.5 nm, from 1 nm to 5 nm, from 1 nm to 4.5 nm,from 1 nm to 4 nm, from 1 nm to 3.5 nm, from 1 nm to 3 nm, from 1 nm to2.5 nm, from 1 nm to 2 nm, or even from 1 nm to 1.5 nm. It should beunderstood that this particle size refers to the particle size of theplatinum nanoparticles on the zeolite, not the particle size of thezeolite with the platinum nanoparticles.

In one or more embodiments, the presently disclosed functionalizedzeolites may be suitable for use as catalysts in refining,petrochemicals, and chemical processing. For example, zeolites may beuseful as cracking catalysts in processes such as hydrocracking or fluidcatalytic cracking. Table 1 shows some contemplated catalyticfunctionality for the presently disclosed functionalized zeolites, andprovides the type of zeolite that may be desirable. However, it shouldbe understood that the description of Table 1 should not be construed aslimiting on the possible uses for functionalized zeolites presentlydisclosed.

Table 1 Catalytic functions of described functionalized zeolitesCatalytic Reaction Target Description Framework of zeolite components ofcatalyst Catalytic cracking To convert high boiling, high molecular masshydrocarbon fractions to more valuable gasoline, olefinic gases, andother products FAU, MFI Hydrocracking To produce diesel with higherquality FAU, BEA Gas oil hydrotreating/Lube hydrotreating Maximizingproduction of premium distillate by catalytic dewaxing FAU, MFI Alkanecracking and alkylation of aromatics To improve octane and production ofgasolines and BTX MFI Olefin oligomerization To convert light olefins togasoline & distillate FER, MFI Methanol dehydration to olefins Toproduce light olefins from methanol CHA, MFI Heavy aromaticstransalkylation To produce xylene from C9+ MFI, FAU Fischer-TropschSynthesis FT To produce gasoline, hydrocarbons, and linearalpha-olefins, mixture of oxygenates MFI CO₂ to fuels and chemicals Tomake organic chemicals, materials, and carbohydrates MFI

According to additional embodiments, the presently disclosedfunctionalized zeolites may be suitable for use in separation and/ormass capture processes. For example, the presently disclosedfunctionalized zeolites may be useful for adsorbing CO₂ and forseparating p-xylene from its isomers.

According to an aspect, either alone or in combination with any otheraspect, a functionalized fibrous hierarchical zeolite includes aframework comprising aluminum atoms, silicon atoms, and oxygen atoms,the framework further comprising a plurality of micropores and aplurality of mesopores. A plurality of nanoparticles comprising platinumare immobilized on the framework.

According to a second aspect, either alone or in combination with anyother aspect, the framework further comprises at least one terminalhydroxyl that forms a dative bond with one or more of the aluminum atomsof the framework.

According to a third aspect, either alone or in combination with anyother aspect, the framework comprises a plurality of silanol groupscomprising at least one of the silicon atoms and at least one of theoxygen atoms.

According to a fourth aspect, either alone or in combination with anyother aspect, at least one oxygen atom of at least one of the pluralityof silanol groups associates with the nanoparticles comprising platinum,thereby immobilizing the nanoparticles comprising platinum.

According to a fifth aspect, either alone or in combination with anyother aspect, the framework is selected from the group consisting of anMFI, an FAU, a BEA, an MOR, and a combination of two or more thereof.

According to a sixth aspect, either alone or in combination with anyother aspect, the framework is an MFI.

According to a seventh aspect, either alone or in combination with anyother aspect, the nanoparticles comprising platinum have an averageparticle size from 1 nm to 10 nm.

According to an eighth aspect, either alone or in combination with anyother aspect, the nanoparticles comprising platinum have an averageparticle size from 1 nm to 5 nm.

According to a ninth aspect, either alone or in combination with anyother aspect, , a method for making a functionalized fibroushierarchical zeolite comprising a plurality of nanoparticles comprisingplatinum includes contacting a functionalized fibrous hierarchicalzeolite comprising isolated terminal organometallic functionalitiescomprising platinum with an atmosphere comprising H₂. The fibroushierarchical zeolite includes a framework comprising aluminum atoms,silicon atoms, and oxygen atoms, the framework further comprising aplurality of micropores and a plurality of mesopores, the fibroushierarchical zeolite being functionalized with at least one terminalhydroxyl. The nanoparticles comprising platinum are immobilized on theframework.

According to a tenth aspect, either alone or in combination with anyother aspect, the framework comprises a plurality of silanol groupsformed by at least one of the silicon atoms and at least one of the atleast one terminal hydroxyl, at least one of the plurality of silanolgroups associating with the nanoparticles comprising platinum, therebyimmobilizing the nanoparticles comprising platinum.

According to an eleventh aspect, either alone or in combination with anyother aspect, the framework is selected from the group consisting of anMFI, an FAU, a BEA, an MOR, and a combination of two or more thereof.

According to a twelfth aspect, either alone or in combination with anyother aspect, the framework is an MFI.

According to a thirteenth aspect, either alone or in combination withany other aspect, the isolated terminal organometallic functionalitiescomprising platinum are selected from the group consisting of a complexof formula (1), a complex of formula (2), a complex of formula (3), acomplex of formula (4), a complex of formula (5), a complex of formula(6), a complex of formula (7), a complex of formula (8), a complex offormula (9), and a combination of two or more thereof, where * denotes apoint of attachment to the oxygen atom of the at least one terminalhydroxyl.

According to a fourteenth aspect, either alone or in combination withany other aspect, the isolated terminal organometallic functionalitiescomprising platinum are a complex of formula (1).

According to a fifteenth aspect, either alone or in combination with anyother aspect, the contacting takes place at a temperature from 300° C.to 700° C.

According to a sixteenth aspect, either alone or in combination with anyother aspect, the contacting takes place for from 1 hours to 5 hours.

EXAMPLES

The various embodiments of methods and systems for formingfunctionalized zeolites will be further clarified by the followingexamples. The examples are illustrative in nature and should not beunderstood to limit the subject matter of the present disclosure.

Example 1 - Synthesis of Mesoporous ZSM-5 Zeolite

A mesoporous ZSM-5 zeolite was formed having a Si/Al molar ratio of 30.In a typical synthesis, a homogeneous solution was prepared bydissolving 0.75 g of NaOH and 0.21 g of NaAlO₂ in 59.0 g of deionizedwater. This was followed by the addition 2.0 g of PDAMAB-TPHAB polymerunder vigorous stirring at 60° C. After stirring for 1 hour, 16.5 g oftetraethyl orthosilicate (TEOS) was added dropwise to the solution andfurther stirred for 12 hours at 60° C. The obtained viscous gel wassubjected to hydrothermal treatment at 150° C. for 60 hours. Theresulting solids were washed, filtered and dried at 110° C. forovernight. The as-synthesized solids were calcined at 550° C. for 6hours at a heating rate of 1° C./min under static conditions. Then, anion-exchange procedure was performed using 1.0 M NH₄NO₃ solution at 80°C. The ion-exchanging process was repeated thrice prior to calcinationat 550° C. for 4 hours in air to generate the H-form of ZSM-5 zeolite.

Example 2 - Synthesis of a ZSM-5 Zeolite Dehydroxylated at 700° C.

A dehydroxylated ZSM-5 zeolite was formed by treating 2 g of themesoporous ZSM-5 zeolite of Example 1 at a temperature of 700° C. and apressure of 10⁻⁵ mbar for a time of 20 hours. Heating occurred at a rateof 150° C./hr.

Example 3 - Synthesis of a Platinum-Containing OrganometallicFunctionalized ZSM-5 Zeolite

The dehydroxylated ZSM-5 zeolite of Example 2 (0.225 mmol of —NH₂concentration, 1 equiv.) was introduced to a first compartment of adouble schlenk flask under an argon atmosphere in a glove box. Asolution of [Pt(COD)(Me)₂] (75 mg, 0.225 mmol, 1 equiv.), which is thecomplex of formula (10), was added to the second compartment of thedouble schlenk flask in dry, degassed benzene (8 mL) at roomtemperature. The [Pt(COD)(Me)₂] solution was transferred to the firstcompartment, and the reaction mixture was stirred at room temperaturefor 20 hours, which led to the formation of a white solid materialidentified as the desired platinum-containing organometallicfunctionalized zeolite. The solid material was isolated from the liquidphase and was washed with dry benzene (3 x 8 mL) to eliminate unreacted[Pt(COD)(Me)₂]. Finally, the platinum-containing organometallicfunctionalized ZSM-5 zeolite was dried at 80° C. under dynamic vacuum(10⁻⁵ mbar) overnight.

The platinum-containing organometallic functionalized ZSM-5 zeolite ofExample 3 was characterized using ¹H-MAS-SS-NMR spectroscopy (400 MHz,25° C.). The ¹H-MAS-SS-NMR spectrum of the platinum-containingorganometallic functionalized ZSM-5 zeolite of Example 3 is displayed inFIG. 2 , which exhibits signals as follows. δ 1.02 [—CH₂ (cod), br],Pt—CH₃ protons (not found, where Pt—Me protons signal overlapped in theupfield region), 2.52 [—CH₂ (cod), br], 3.22 (unreacted[(≡Al←OH—Si≡]br), 4.78 [(—CH═CH— )(cod), br], 6.48 [(—CH═CH—) (cod),br].

The platinum-containing organometallic functionalized ZSM-5 zeolite ofExample 3 was characterized using ¹³C-CP-MAS-SS-NMR spectroscopy (100MHz, 25° C.). The ¹³C{¹H} CP-MAS-SS-NMR spectrum of theplatinum-containing organometallic functionalized ZSM-5 zeolite ofExample 3 is displayed in FIG. 3 , which exhibits signals as follows. δ115.1 (C═C), δ 74.5 (C═C), δ 30.4 (C_(H2)), 28.2 (C_(H2)) and 4.4 ppm(CH3).

The platinum-containing organometallic functionalized ZSM-5 zeolite ofExample 4 was analyzed by ²⁷Al-SS-NMR spectroscopy (234.6 MHz, 25° C.).The ²⁷Al-SS-NMR spectrum of the platinum-containing organometallicfunctionalized ZSM-5 zeolite of Example 3 is displayed in FIG. 4 , whichexhibits a peak at δ 55.53 ppm (Aliv) and 2.61 ppm (Al_(VI)).

Example 4 - Synthesis of a Platinum Nanoparticle Functionalized ZSM-5Zeolite

The platinum-containing organometallic functionalized ZSM-5 zeolite ofExample 3 (500 mg) was placed in a quartz tube under a dynamic hydrogenflow (5 % H₂ in Ar) at 500° C. for 2 h. The temperature program was setto 500° C./hour. The furnace was cooled to room temperature in the sameflow. Then, the resulting material was collected and determined to bethe platinum-nanoparticle functionalized ZSM-5 zeolite, which was storedin the glove box for further characterization.

X-ray photoelectron spectroscopy (XPS) of the platinum-nanoparticlefunctionalized ZSM-5 zeolite of Example 4 is shown in FIG. 5 (Al 2p andPt 41) and FIG. 6 (Pt 4d). In X-ray Photoelectron Spectroscopy (XPS),the platinum oxidation states can be analyzed from the binding energies(BE) and the chemical shift of the Pt 4f and Pt 4d photoelectron linesin XPS spectra. As shown in FIG. 5 , the binding energy signal of Pt 4f7/2 at 71.3 eV corresponds to a Pt(0) atom in the material, and thus,the binding energy signal of Pt 4f 5/2 overlapped with aluminosilicateas Al 2p 3/2 around 74.5 eV. Additionally, the binding energy signals ofPt 4d 3/2 and Pt 4d 5/2 are 315.1 and 332.0 eV that correspond to thePt(0) atom in the material, as shown in FIG. 6 .The XPS experiments wereperformed on a Kratos Axis Ultra DLD instrument equipped with amonochromatic Al Kα x-ray source (hv = 1486.6 eV) operated at a power of75 W and under UHV conditions in the range of ~ 10⁻⁹ mbar. All spectrawere recorded in hybrid mode using electrostatic and magnetic lenses andan aperture slot of 300 µm × 700 µm . The survey and high-resolutionspectra were acquired at fixed analyzer pass energies of 160 eV and 20eV, respectively. The samples were mounted in floating mode in order toavoid differential charging. Therefore, XPS spectra were acquired usingcharge neutralization. Because the samples are air-sensitive, they weretransferred to the XPS instrument and analyzed without exposing them tothe ambient air. For this purpose, samples were first prepared insidethe glovebox always kept under argon atmosphere and were subsequentlytransferred to the XPS instrument using a special transfer chamberfilled with argon prior to be sealed. The samples were promptly analyzedafter being loaded into the instrument.

The microscopic observations of the platinum-nanoparticle functionalizedZSM-5 zeolite of Example 4 were performed under an inert atmosphereusing scanning transmission electron microscopy (HAADF-STEM), as shownin FIG. 7 . This experiment confirms the presence of platinum andcarbon, which are displayed on the surface of the platinum-nanoparticlefunctionalized ZSM-5 zeolite of Example 4. High-resolution transmissionelectron microscopy (HR-TEM) images, FIG. 8 , of theplatinum-nanoparticle functionalized ZSM-5 zeolite of Example 4 clearlyshow the lattice fringes originating from the MFI framework, whichremains unchanged from the dehydroxylated ZSM-5 zeolite of Example 2.FIG. 9 provides the particle size distribution of theplatinum-nanoparticles present on a platinum-nanoparticle functionalizedZSM-5 zeolite for the corresponding scanning transmission electronmicroscopy image. The average particle size was found to be about 1.9nm. Transmission electron microscopy (TEM) and scanning TEM (STEM)investigations were performed with a ThermoFisher FEI Titan 80-300 Cubedmicroscope equipped with a high-brilliance field emission gun (300 kV),a Wien-type FEI monochromator, chemiSTEM™ technology for energydispersive X-ray spectroscopy (EDX), and a CEOS spherical aberrationprobe corrector (for the condenser lens system) allowing a finalresolution of 0.9 Å in STEM mode. The TEM samples were fully prepared ina glove box under an argon inert atmosphere to avoid any alterationreaction due to the exposure to the air and then transferred directlyinto a Gatan 618 double-tilt vacuum transfer holder. In that way, thesamples were never exposed to the air from the synthesis to theanalysis.

Having described the subject matter of the present disclosure in detailand by reference to specific embodiments, it is noted that the variousdetails described in this disclosure should not be taken to imply thatthese details relate to elements that are essential components of thevarious embodiments described in this disclosure, even in cases where aparticular element is illustrated in each of the drawings that accompanythe present description. Rather, the claims appended hereto should betaken as the sole representation of the breadth of the presentdisclosure and the corresponding scope of the various embodimentsdescribed in this disclosure. Further, it will be apparent thatmodifications and variations are possible without departing from thescope of the appended claims.

The singular forms “a”, “an” and “the” include plural referents, unlessthe context clearly dictates otherwise.

For the purposes of describing and defining the present disclosure it isnoted that the term “about” is utilized in this disclosure to representthe inherent degree of uncertainty that may be attributed to anyquantitative comparison, value, measurement, or other representation.The term “about” is also utilized in this disclosure to represent thedegree by which a quantitative representation may vary from a statedreference without resulting in a change in the basic function of thesubject matter at issue.

As used in this disclosure and in the appended claims, the words“comprise,” “has,” and “include” and all grammatical variations thereofare each intended to have an open, non-limiting meaning that does notexclude additional elements or steps.

Additionally, the term ”consisting essentially of”is used in thisdisclosure to refer to quantitative values that do not materially affectthe basic and novel characteristic(s) of the disclosure. For example, achemical stream “consisting essentially” of a particular chemicalconstituent or group of chemical constituents should be understood tomean that the stream includes at least about 99.5% of a that particularchemical constituent or group of chemical constituents.

It should be understood that any two quantitative values assigned to aproperty may constitute a range of that property, and all combinationsof ranges formed from all stated quantitative values of a given propertyare contemplated in this disclosure.

As used in this disclosure, terms such as “first” and “second” arearbitrarily assigned and are merely intended to differentiate betweentwo or more instances or components. It is to be understood that thewords “first” and “second” serve no other purpose and are not part ofthe name or description of the component, nor do they necessarily definea relative location, position, or order of the component. Furthermore,it is to be understood that the mere use of the term “first” and“second” does not require that there be any “third” component, althoughthat possibility is contemplated under the scope of the presentdisclosure.

1. A functionalized fibrous hierarchical zeolite comprising a frameworkcomprising aluminum atoms, silicon atoms, and oxygen atoms, theframework further comprising a plurality of micropores and a pluralityof mesopores, wherein: a plurality of nanoparticles comprising platinumare immobilized on the framework.
 2. The functionalized fibroushierarchical zeolite of claim 1, wherein the framework further comprisesat least one terminal hydroxyl that forms a dative bond with one or moreof the aluminum atoms of the framework.
 3. The functionalized fibroushierarchical zeolite of claim 1, wherein the framework comprises aplurality of silanol groups comprising at least one of the silicon atomsand at least one of the oxygen atoms.
 4. The functionalized fibroushierarchical zeolite of claim 3, wherein at least one oxygen atom of atleast one of the plurality of silanol groups associates with thenanoparticles comprising platinum, thereby immobilizing thenanoparticles comprising platinum.
 5. The functionalized fibroushierarchical zeolite of claim 1, wherein the framework is selected fromthe group consisting of an MFI, an FAU, a BEA, an MOR, and a combinationof two or more thereof.
 6. The functionalized fibrous hierarchicalzeolite of claim 1, wherein the framework is an MFI.
 7. Thefunctionalized fibrous hierarchical zeolite of claim 1, wherein thenanoparticles comprising platinum have an average particle size from 1nm to 10 nm.
 8. The functionalized fibrous hierarchical zeolite of claim1, wherein the nanoparticles comprising platinum have an averageparticle size from 1 nm to 5 nm.
 9. A method for making a functionalizedfibrous hierarchical zeolite comprising a plurality of nanoparticlescomprising platinum, the method comprising: contacting a functionalizedfibrous hierarchical zeolite comprising isolated terminal organometallicfunctionalities comprising platinum with an atmosphere comprising H₂,wherein the fibrous hierarchical zeolite comprises: a frameworkcomprising aluminum atoms, silicon atoms, and oxygen atoms, theframework further comprising a plurality of micropores and a pluralityof mesopores, the fibrous hierarchical zeolite being functionalized withat least one terminal hydroxyl; wherein the nanoparticles comprisingplatinum are immobilized on the framework, thereby producingfunctionalized fibrous hierarchical zeolite comprising a plurality ofnanoparticles comprising platinum.
 10. The method of claim 9, whereinthe framework comprises a plurality of silanol groups formed by at leastone of the silicon atoms and at least one of the at least one terminalhydroxyl, at least one of the plurality of silanol groups associatingwith the nanoparticles comprising platinum, thereby immobilizing thenanoparticles comprising platinum.
 11. The method of claim 9, whereinthe framework is selected from the group consisting of an MFI, an FAU, aBEA, an MOR, and a combination of two or more thereof.
 12. The method ofclaim 9, wherein the framework is an MFI.
 13. The method of claim 9,wherein the isolated terminal organometallic functionalities comprisingplatinum are selected from the group consisting of a complex of formula(1), a complex of formula (2), a complex of formula (3), a complex offormula (4), a complex of formula (5), a complex of formula (6), acomplex of formula (7), a complex of formula (8), a complex of formula(9), and a combination of two or more thereof, where * denotes a pointof attachment to the oxygen atom of the at least one terminal hydroxyl.

.
 14. The method of claim 9, wherein the isolated terminalorganometallic functionalities comprising platinum are a complex offormula (1).
 15. The method of claim 9, wherein the contacting takesplace at a temperature from 300° C. to 700° C.
 16. The method of claim9, wherein the contacting takes place for from 1 hours to 5 hours.